Nik Wallenda knows death haunts every step he takes on the high wire. As the great grandson of Karl Wallenda -- the German emigre and patriarch of the Flying Wallendas who perished in 1978 on a wire badly strung between two towers of the Condado Plaza hotel in San Juan, Puerto Rico -- he also knows that some of the millions of viewers who have tuned in to his treacherous traverses of Niagara Falls and the Grand Canyon are waiting for a snuff film. "I'm sure there's a percentage saying, 'I hope he falls,' " says Wallenda.

Nevermind that ABC and Discovery aired the Niagara and Canyon walks on 10-second delays with production contingencies stipulating that cameras would not show the worst. The specter of danger on live (or virtually live) TV has made Wallenda and his fellow stunt professionals highly sought after by network executives eager for content that can be eventized for maximum ratings potential in an increasingly time-shifted media universe.

"In the cable landscape, live is the event strategy," says Eileen O'Neill, group president of Discovery Channel, Science Channel and Velocity. "A lot of our storytelling is very much in the moment."

"I'm sure there's a percentage [of viewers] saying 'I hope he falls,'" said Wallenda, on his treacherous traverses on live television.

Such white-knuckle television has become a ratings boom: ABC's broadcast of Wallenda's Niagara Falls walk in June 2012 peaked with more than 10 million viewers, while last summer, 13 million people watched Discovery's coverage of his 23-minute walk over the Grand Canyon's Little Colorado Gorge -- 1,500 feet above the ground. Austrian jumper Felix Baumgartner's record-breaking skydive from the stratosphere in December 2012 brought Discovery 4.2 million viewers, a network record for the sleepier daytime hours. Even advertisers, a cautious group in general, have been won over -- mostly. Mitsubishi and GoPro cameras ponied up millions for 360-sponsorship deals on the Grand Canyon walk; GoPro returns for Discovery's Everest Jump Live special in May, in which climber and wing-suit jumper Joby Ogwyn will jump from the summit of Everest in a custom-made wing suit. And the network also has signed up Falkan Tire, which will get branding on Ogwyn's suit.

"Honestly, it's not for every client," admits Discovery ad sales president Joe Abruzzese. "One client said, 'I don't want to be on a YouTube clip where my [logo] is on Wallenda as he's going down into the Colorado River.' Nik promised us he wouldn't fall. And Joby said, 'I can land in a teacup.' We have a lot more clients that want in than we have saying, 'I won't touch this.' "

Wallenda and Discovery are readying another high-wire walk. This one, says Wallenda cryptically, will be in "an urban environment." And in the fall, NatGeo will air world champion free diver William Trubridge's attempt at a new record: a 350-foot dive (that's twice the height of the Statue of Liberty) on a single breath. The entire dive -- which will take place in the Bahamas -- will last about 4½ minutes. And the network still is working on a live broadcast of free climber Alex Honnold scaling a 1,667-foot Taipei skyscraper -- without safety lines, naturally.

Evel Knievel became a folk hero and arguably the first daredevil TV star in 1967, when he hurtled his motorcycle over the fountains at Caesars Palace in Las Vegas -- and landed in a spectacular crash. And YouTube has been awash in jackass stunts almost since its inception. The current revival has been spurred by the chase for live TV. And it inevitably has brought the crazies out of the woodwork. One producer recalls a pitch from a man who wanted to chain himself into a coffin and have it dropped 30,000 feet from an airplane while he attempted to free himself from his chains and parachute safely to the ground. Sharon Scott, president of Peacock Productions, which produced Wallenda's Grand Canyon walk and Discovery's Everest Jump Live, says free-climb pitches are common.

"It may be the worst idea ever, but people are so desperate to be on television they may try to convince you that it's all great," she says.

National Geographic executives are on the receiving end of myriad Houdini-esque stunts. "People are really into live everything. They just want to turn any kind of show into live and think that it's going to make magic," notes Heather Moran, executive vp programming. "We need to have that extra exploration element."

Mounting such productions comes with novel challenges. There will be a 100-person production team for Ogwyn's Everest ascent and jump including four cameramen, all but one of whom has scaled Everest as least once. Yaks will take hundreds of pounds of equipment up the mountain including about 200 camera batteries because lithium camera batteries do not last as long in cold temperatures. Each cameraman will have at least two sherpas to carry gear including tripods, lenses, receivers and antennas. Once Ogwyn and his expedition leader reach the summit, one of the sherpas will have to stand with a handheld antenna and make sure it's pointing at a receiver.

"They'll have to hit these repeaters so the line of sight has to be exact," explains Howard Swartz, Discovery's vp production. "And if you've ever looked at a schematic of Everest, there are a lot of potential black holes."

There are scripts for the anchors in the event they have to shift into breaking news mode. And if Ogwyn's team encounters a dead body on the ascent? "We will want to be tasteful and sensitive to that," adds Swartz. "It's not our desire or intent to linger on something like that."

More than 200 people have died on Everest and many of their bodies remain there, preserved for decades by the sub-zero temperatures.

"These projects come to us from people who want to do this," adds O'Neill. "How they want to set up the event is up to them. I'm not a person who can string cable, nor can I climb Everest. We make TV. We really do rely heavily on the person doing the stunt for logistics."

And being a tightrope walker or a free diver means you probably carry your own insurance rider. Notes Wallenda, "I have enormous insurance bills." And he wouldn't have it any other way. Wallenda, 35, says he has been on the wire longer than he has been alive -- his mother walked the wire when she was pregnant with him -- and has yet to be seriously injured. He has been known to feign slipping and hints that's exactly what he did during a walk over Baltimore's Inner Harbor three weeks before he was due to traverse Niagara Falls for ABC's live special. "I'm a showman, and I'll leave it at that," he says. "But ABC [executives] saw that, and it freaked them out."

"Evel Knievel was one of my great grandfather's best friends. When he did those jumps, we wanted him to survive. But we wanted to make sure we were watching in case he didn't. And I think that's what it comes down to with me. That's just human nature," says Wallenda, photographed March 28 at the Circus Arts Conservatory Tent in Sarasota, Fla.

And so he was forced to wear a tether over the falls, which he says runs counter to more than half a century of Wallenda family tradition.

"I train for worst case," says Wallenda. "I trained during a tropical storm with 67-mile-per-hour winds and a torrential downpour [on a cable lower to the ground]. I've trained my whole life to grab that wire. That wire right at my feet is always a safe haven."